Abstract
Precise control of domain wall displacement in nanowires is essential for application in domain wall based memory and logic devices. Currently, domain walls are pinned by creating topographical notches fabricated by lithography. In this paper, we propose localized diffusion of non-magnetic metal into ferromagnetic nanowires by annealing induced mixing as a non-topographical approach to form pinning sites. As a first step to prove this new approach, magnetodynamic properties of permalloy (Ni80Fe20) films coated with different capping layers such as Ta, Cr, Cu and Ru were investigated. Ferromagnetic resonance (FMR), and anisotropy magnetoresistance (AMR) measurements were carried out after annealing the samples at different temperatures (Tan). The saturation magnetization of Ni80Fe20 film decreased, and damping constant increased with Tan. X-Ray photoelectron spectroscopy results confirmed increased diffusion of Cr into the middle of Ni80Fe20 layers with Tan. The resistance vs magnetic field measurements on nanowires showed intriguing results.
Highlights
Domain wall based devices such as racetrack memory have been proposed as promising candidates for high-density, non-volatile information storage with a low energy consumption[1,2,3,4,5,6,7,8,9]
The torque exerted by in-plane current named as spin transfer torque (STT), drove domain wall motion in the opposite direction of electric current flow, and is often considered as an effective field[19,20]
The pure spin polarized current originates from the electric current in heavy metal due to strong spin orbit coupling and Rashba effect, which is named as spin orbit torque (SOT)[23,24]
Summary
Domain wall based devices such as racetrack memory have been proposed as promising candidates for high-density, non-volatile information storage with a low energy consumption[1,2,3,4,5,6,7,8,9]. The theory for spin-transfer torque was reported by Berger and Slonczewski in 1996 They pointed out that a spin polarized current is generated when an electric current that goes through the ferromagnetic layer transfers the spin angular momentum to local magnetic moment via electron exchange interaction. The torque exerted by in-plane current named as spin transfer torque (STT), drove domain wall motion in the opposite direction of electric current flow, and is often considered as an effective field[19,20]. In those cases, the velocity of domain wall was just 100 m/s19,20. The Ni80Fe20 devices with cross pinning sites have been fabricated to show that this method could be useful in domain wall pinning
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